SIMSCRIPT II.5 Programming Language

SIMSCRIPT II.5 Programming Language
3.4.2 The Formatted I/O Statements READ and Write
As described in Chapter 1, input and output data streams consist of a sequence of records, corresponding
to lines of printed output or lines of data accepted from a terminal. Each record, in turn,
is composed of a sequence of fields. A field is a logically defined group of consecutive symbols.
In free-form data, a field is delimited by blank characters. In print output statements, an output
field position within a printed line may be defined by asterisks. This latter facility may be extended
to provide greater program-directed control over the structuring of both input and output records.
A read statement that accepts formatted data has the form:
read variable list as format list
in which each variable value to be read has its input data format field described by a corresponding
field descriptor character in a format list. These formats, which are codes describing how the fields
in the input data stream are composed, are described in the next subsection.
The write statement transfers values from within the computer to specified external media. Every
write statement is formatted. With the sole exception of the list statement, the programmer is
always required to indicate the arrangement of output data. The write statement looks like the
read statement. Its form is:
write expression list as format list
The indicated expressions, which may simply be variables, are evaluated and printed in the form
described by their matching format descriptors. Before illustrating these read and write statements
with examples, the format descriptors are defined.
3.4.2.1 I (Integer) Descriptor
A descriptor of the form n I w is used for converting numbers from their internal integer computer
storage representation to an external format, and vice versa. The character I is always followed by
an expression (w), specifying the maximum number of digits in the integer field, including the sign.
The I can be preceded by a number (n), declaring that the descriptor defines n consecutive identical
data fields. Such formats as 2 I 6 and 14 I 3 define 2 fields of 6 positions and 14 fields of 3
positions, respectively. There must be at least one blank between the fields n, I, w.
When an I format is used for input, it specifies that the full contents of a field w digits wide are to
be stored as the value of a corresponding variable in a read statement. Blank field positions —
leading, embedded, or trailing — are treated as zeros. If a field is unsigned, it is interpreted as positive,
although a plus sign can be typed. Except for the sign character, only numbers can be typed
in a I data field. If w is larger than the maximum number of digits that can be stored in a computer
word, only the rightmost, storable digits are used.
On output, an I format places a right-justified integer value in a field of specified width. Numbers
larger than the field width are converted to scientific notation (see paragraph 3.4.2.3). Positive
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